The present invention relates to fiber optics. More particularly, the present invention relates to a technique for precise alignment and attachment of fiber optics to planar lightwave circuits (PLCs).
Fiber optic communication links employ in-line, optical components for various operations including amplification, attenuation, multiplexing, demultiplexing, etc. These components are often formed from planar lightwave circuits (PLCs), within which various structures are used to perform the requisite optical signal processing operations.
PLCs are usually wafer-based modules formed using various silicon-based semiconductor formation techniques including growth, deposition and etching. The upper layers of PLCs usually employ waveguides (e.g., silica-on-silicon), deposited and etched, through which the optical signals are transmitted. For effective use in fiber optic systems, the PLC waveguides must be interfaced to fiber optics, which carry the optical signals to and from the PLC.
To ensure quality signal transmission to and from the PLC, the fiber optics must be precisely aligned to the PLC waveguides. Any misalignment will result in signal insertion loss, which is highly undesirable in optical networks because it directly impacts the distance over which the optical signals can travel. Equally important are the techniques used to attach the fiber optics to the PLC. Rigid attachment is required to maintain alignment over the life of the component, and through various environmental conditions. The techniques chosen for alignment and attachment are highly interrelated since they will be implemented on the same sub-assembly, and thus must be carefully, and compatibly implemented, while keeping the costs of the sub-assembly to acceptable levels.
What is required, therefore, are improved techniques for aligning and attaching fiber optics to PLC waveguides, which are compatible and which can be implemented at reasonable costs.
These requirements are met, and further advantages are provided, by the present invention which in one aspect is a groove assembly for holding at least one fiber optic, and methods for its fabrication and use. The assembly includes a base, a cover and a carrier disposed between the base and the cover. The carrier has at least one groove. At least one fiber optic is disposed in this groove, and therefore between the carrier and the base or cover, and terminates at an edge surface of the carrier. The base and cover have respective edge surfaces serving as attachment surfaces for attachment of the groove assembly to a device with at least one waveguide terminating at an edge thereof, to which the fiber (or array of fibers) is to be aligned.
The base and/or cover are preferably formed from a first material enabling attachment of the assembly to the device, e.g., a material transparent to energy to be directed through the material for curing an adhesive used to adhere the respective edge surfaces of the base and cover to the device. The carrier is formed from a second material enabling a substantially more precise formation of the grooves than would the first material, e.g., silicon, which enables precise formation of the grooves.
The assembly is especially adapted for attachment to the edge of a planar lightwave circuit (PLC). The PLC has at least one waveguide running to the edge thereof, and the assembly is attached via the respective edge surfaces of the base and cover, and respective mating surfaces of the PLC, using an adhesive, such that the fiber optic is aligned to the waveguide. The PLC may also include a block, to form one of the mating surfaces. This block may also be formed from a material transparent to energy to be directed through the material for curing the adhesive.
The combination of the small silicon carrier, between the transparent base and cover, offers distinct advantages over prior techniques. High precision groove formation is possible in the silicon, thus improving optical performance. The small piece of silicon (5 mm vs. 12 mm) decreases costs. Finally, larger, transparent base and cover pieces provide at least two adhesion points and other structural integrity.